Extrusion Blow-Molded Articles and Process for Their Production

ABSTRACT

The present application relates to extrusion blow-molded articles comprising a polypropylene layer, said polypropylene layer consisting of a polypropylene composition comprising a specific random copolymer of propylene and at least one comonomer. The present application also relates to a process for the production of such extrusion blow-molded articles.

FIELD OF THE INVENTION

The present application relates to extrusion blow-molded articlescomprising a polypropylene layer, said polypropylene layer consisting ofa polypropylene composition comprising a specific random copolymer ofpropylene and at least one comonomer. The present application alsorelates to a process for the production of such extrusion blow-moldedarticles.

THE TECHNICAL PROBLEM AND THE PRIOR ART

Generally, in the extrusion blow-molding process a parison is formed bymelt-extruding a molten polymer composition (preferably in a downwarddirection), clamped into a mold, expanded by gas pressure to obtain anexpanded parison corresponding to the shape of the mold, cooled, ejectedfrom the mold and optionally trimmed as necessary.

Depending on whether the extrusion is done continuously or not, one maydistinguish between a continuous extrusion blow-molding process or anintermittent extrusion blow-molding process. In the continuous process,the molten polymer is extruded continuously from the extruder and two ormore molds must shuttle back and forth between the parison drop area,where the parison is captured and clamped into the mold, and a coolingarea, where the parison is expanded by gas pressure, cooled and finallyejected. In the intermittent process a single (stationary) mold is usedand the extruder is equipped with an accumulator head, which allows tocollect molten polymer composition.

Due to the fact that the parison must hold while it is being extrudeduntil the mold captures and clamps it, polymer compositions used inextrusion blow-molding must have good melt strength. For this reasoncommercially available polypropylene grades are characterized by lowmelt flow indices. Generally, the melt flow index of commercialextrusion blow-molding grades are very low so as to result in sufficientmelt strength to be suited for extrusion blow-molding.

However, industry remains further interested in improving theprocessability and/or throughput of polypropylene in extrusionblow-molding, while at the same time keeping the properties of theextrusion blow-molded article at a sufficient level.

It is therefore an object of the present application to provide anextrusion blow-molding process for the production of an extrusionblow-molded article, allowing said article to be produced with goodprocessability.

Additionally, it is an object of the present application to provide anextrusion blow-molding process for the production of an extrusionblow-molded article, said process resulting in reduced energyconsumption.

Furthermore, it is an object of the present application to provide anextrusion-blow molding process for the production of an extrusionblow-molded article, said process having increased throughput.

It is a further object of the present application to provide anextrusion blow-molded article having acceptable mechanical properties.

It is also an object of the present application to provide an extrusionblow-molded article having acceptable optical properties.

BRIEF DESCRIPTION OF THE INVENTION

The inventors named in the present application have surprisingly foundthat any one of these objects can be attained either individually or inany combination by providing an extrusion blow-molded article consistingof a polypropylene composition, said polypropylene compositioncomprising a well-defined random copolymer of propylene and at least onecomonomer.

Thus, the present application provides for an extrusion blow-moldedarticle comprising a polypropylene layer, said polypropylene layerconsisting of a polypropylene composition comprising a random copolymerof propylene and at least one comonomer, wherein the random copolymerhas a molecular weight distribution, defined as M_(w)/M_(n), of at most4.0, a percentage of 2,1-insertions of at least 0.1%, relative to thetotal number of propylene molecules in the chain, and comprises at most7.0 wt %, relative to the total weight of said random copolymer, of theat least one comonomer.

The present application also provides for a process for the productionof an extrusion blow-molded article, said process comprising the stepsof

(a) polymerizing propylene and at least one comonomer with ametallocene-based polymerization catalyst to obtain a random copolymerof propylene and at least one comonomer, wherein the random copolymercomprises at most 7.0 wt %, relative to the total weight of said randomcopolymer, of the at least one comonomer;

(b) melt-extruding a polypropylene composition comprising the randomcopolymer prepared in step (a) to form a parison of said moltenpolypropylene composition;

(c) clamping the parison into a mold so that the parison is closed offat both ends to form a clamped-off parison;

(d) injecting a gas under pressure into said clamped-off parison toobtain an expanded parison having the shape of the mold;

(e) finally cooling and ejecting the extrusion blow-molded article.

Furthermore, the present application provides for the use of saidextrusion blow-molded article in packaging applications.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the present application the terms “polypropylene” and“propylene polymer” may be used synonymously.

Throughout the present application the term “propylene random copolymer”may be used to denote a “random copolymer of propylene and at least onecomonomer”. The term “metallocene propylene random copolymer” may beused to denote a “random copolymer of propylene and at least onecomonomer having been produced with a metallocene-based polymerizationcatalyst”.

Throughout the present application the melt flow index, abbreviated as“MFI”, of polypropylene and polypropylene compositions is determinedaccording to ISO 1133, condition L, at 230° C. and 2.16 kg.

Throughout the present application the term “tetrahydroindenyl”signifies an indenyl group wherein the six-membered ring has beenhydrogenated to form 4,5,6,7-tetrahydroindenyl.

In general terms, the present application provides for an extrusionblow-molded article comprising a polypropylene layer as defined in thefollowing. Preferably, said extrusion blow-molded article is acontainer, which can be used e.g. for the storage and transport of, forexample, liquids or powders or gels or particulate materials. Morepreferably, said extrusion blow-molded container is a bottle, having, byway of non-limiting example, a round, oval or square shape. Saidextrusion blow-molded article can also be with or without a handle. Theextrusion blow-molded article has a preferred volume from a fewmilliliters, for example 5 or 10 or 50 or 100 ml, to at most 1 l or 5 lor 10l.

Preferably, the extrusion blow-molded article has a wall thickness of atleast 300 μm, more preferably of at least 400 μm, even more preferablyof at least 500 μm, and most preferably of at least 600 μm. Preferably,the wall thickness of the extrusion blow-molded article is at most 2000μm, more preferably at most 1500 μm or 1400 μm, even more preferably atmost 1300 μm or 1200 μm, still even more preferably at most 1100 μm, andmost preferably at most 1000 μm.

Polypropylene Composition

The polypropylene composition, of which the polypropylene layerconsists, comprises a random copolymer of propylene and at least onecomonomer. For the purpose of the present application it is essentialthat said random copolymer of propylene and at least one comonomer hasbeen produced with a metallocene-based polymerization catalyst, i.e. isa metallocene propylene random copolymer. It is further essential thatsaid random copolymer of propylene and at least one comonomer comprisesat most 7.0 wt %, relative to the total weight of the random copolymer,of the at least one comonomer.

Preferably, the polypropylene composition comprises at least 50 wt % or70 wt %, more preferably at least 80 wt % or 90 wt %, even morepreferably at least 95 wt % or 97 wt %, and still even more preferablyat least 99 wt %, relative to the total weight of said polypropylenecomposition, of the metallocene propylene random copolymer. Mostpreferably, said polypropylene composition consists of the metallocenepropylene random copolymer. The remainder of said polypropylenecomposition may be one or more thermoplastic polymers as defined below.

Preferably, the metallocene propylene random copolymer comprises atleast 0.5 wt %, more preferably at least 1.0 wt %, even more preferablyat least 1.5 wt %, and most preferably at least 2.0 wt %, relative tothe total weight of said metallocene propylene random copolymer, of theat least one comonomer. Preferably, the metallocene propylene randomcopolymer comprises at most 7.0 wt %, relative to the total weight ofsaid random copolymer, of the at least one comonomer, more preferably atmost 6.0 wt % or 5.0 wt % or 4.5 wt %, even more at most 4.0 wt %, stilleven more preferably at most 3.5 wt %, and most preferably at most 3.0wt %.

Preferably, the metallocene propylene random copolymer of propylene andat least one comonomer is a random copolymer of propylene and at leastone alpha-olefin different from propylene. Preferred alpha-olefins areethylene, butene-1, pentene-1, hexene-1 and 4-methyl-pentene-1. Morepreferred alpha-olefins are ethylene, butene-1 and hexene-1. The mostpreferred alpha-olefin is ethylene. Thus, the most preferred propylenerandom copolymer used herein is a random copolymer of propylene andethylene.

Preferably, the metallocene propylene random copolymer used herein has amelt flow index of at least 3.0 dg/min, more preferably of at least 4.0or 5.0 dg/min, even more preferably of at least 6.0 dg/min, still evenmore preferably of at least 7.0 dg/min, and most preferably of at least8.0 dg/min. Preferably, the metallocene propylene random copolymer has amelt flow index of at most 25 dg/min, more preferably of at most 20dg/min, even more preferably of at most 18 dg/min, still even morepreferably of at most 16 dg/min, and most preferably of at most 14dg/min.

The metallocene propylene random copolymer used herein has a molecularweight distribution, defined as M_(w)/M_(n), i.e. the ratio of weightaverage molecular weight M_(w) over number average molecular weightM_(n), of at most 4.0. Preferably, the metallocene propylene randomcopolymer used herein has a molecular weight distribution, defined asM_(w)/M_(n), of at most 3.5, more preferably of at most 3.0, and mostpreferably of at most 2.8. Preferably, the metallocene propylene randomcopolymer used herein has a molecular weight distribution (MWD), definedas M_(w)/M_(n), of at least 1.0, more preferably of at least 1.5 andmost preferably of at least 2.0. Molecular weights can be determined bysize exclusion chromatography (SEC) as described in the test methods.

Preferably, the metallocene propylene random copolymer used herein ischaracterized by high isotacticity, for which the content of mmmmpentads is a measure. Preferably, the content of mmmm pentads is atleast 90%, more preferably at least 95%, and most preferably at least97%. The isotacticity may be determined by ¹³C-NMR analysis as describedin the test methods.

The metallocene propylene random copolymer used herein is characterizedby a percentage of 2,1-insertions, relative to the total number ofpropylene molecules in the polymer chain, of at least 0.1%. Preferably,the percentage of 2,1-insertions is at most 1.5%, more preferably atmost 1.3%, even more preferably at most 1.2%, still even more preferablyat most 1.1%, and most preferably at most 1.0%. The percentage of2,1-insertions may be determined as indicated in the test methods.

Preferably, the metallocene propylene random copolymer used hereincomprises at least two propylene polymer fractions, which may differ intheir respective comonomer content or in their respective melt flowindex or in both, provided that the properties of the metallocenepropylene random copolymer are as given above.

The metallocene propylene random copolymer used herein is obtained bypolymerizing propylene and at least one comonomer with ametallocene-based polymerization catalyst. Preferably themetallocene-based polymerization catalyst comprises a bridgedmetallocene component, a support and an activating agent. Suchmetallocene-based polymerization catalysts are generally known in theart and need not be explained in detail.

The metallocene component can be described by the following generalformula

(μ-R^(a))(R^(b))(R^(c))MX¹X²  (I)

wherein R^(a), R^(b), R^(c), M, X¹ and X² are as defined below.

R^(a) is the bridge between R^(b) and R^(c), i.e. R^(a) is chemicallyconnected to R^(b) and R^(c), and is selected from the group consistingof —(CR¹R²)_(p)—, —(SiR¹R²)_(p)—, —(GeR¹R²)_(p)—, —(NR¹)_(p)—,—(PR¹)_(p)—, —(N⁺R¹R²)_(p)— and —(P⁺R¹R²)_(p)—, and p is 1 or 2, andwherein R¹ and R² are each independently selected from the groupconsisting of hydrogen, C₁-C₁₀ alkyl, C₅-C₈ cycloalkyl, C₆-C₁₅ aryl,alkylaryl with C₁-C₁₀ alkyl and C₆-C₁₅ aryl, or any two neighboring R(i.e. two neighboring R¹, two neighboring R², or R¹ with a neighboringR²) may form a cyclic saturated or non-saturated C₄-C₁₀ ring; each R¹and R² may in turn be substituted in the same way. Preferably R^(a) is—(CR¹R²)_(p)— or —(SiR¹R²)_(p)— with R¹, R² and p as defined above. Mostpreferably R^(a) is —(SiR¹R²)_(p)— with R¹, R² and p as defined above.Specific examples of R^(a) include Me₂C, ethanediyl (—CH₂—CH₂—), Ph₂Cand Me₂Si.

M is a metal selected from Ti, Zr and Hf, preferably it is Zr.

X¹ and X² are independently selected from the group consisting ofhalogen, hydrogen, C₁-C₁₀ alkyl, C₆-C₁₅ aryl, alkylaryl with C₁-C₁₀alkyl and C₆-C₁₅ aryl. Preferably X¹ and X² are halogen or methyl.

R^(b) and R^(c) are selected independently from one another and comprisea cyclopentadienyl ring.

Preferred examples of halogen are Cl, Br, and I. Preferred examples ofC₁-C₁₀ alkyl are methyl, ethyl, n-propyl, iso-propyl, n-butyl,iso-butyl, and tert-butyl. Preferred examples of C₅-C₇ cycloalkyl arecyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Preferred examplesof C₆-C₁₅ aryl are phenyl and indenyl. Preferred examples of alkylarylwith C₁-C₁₀ alkyl and C₆-C₁₅ aryl are benzyl (—CH₂—Ph), and —(CH₂)₂—Ph.

Preferably, R^(b) and R^(c) may both be substituted cyclopentadienyl, ormay be independently from one another unsubstituted or substitutedindenyl or tetrahydroindenyl, or R^(b) may be a substitutedcyclopentadienyl and R^(c) a substituted or unsubstituted fluorenyl.More preferably, R^(b) and R^(c) may both be the same and may beselected from the group consisting of substituted cyclopentadienyl,unsubstituted indenyl, substituted indenyl, unsubstitutedtetrahydroindenyl and substituted tetrahydroindenyl. By “unsubstituted”is meant that all positions on R^(b) resp. R^(c), except for the one towhich the bridge is attached, are occupied by hydrogen. By “substituted”is meant that, in addition to the position at which the bridge isattached, at least one other position on R^(b) resp. R^(c) is occupiedby a substituent other than hydrogen, wherein each of the substituentsmay independently be selected from the group consisting of C₁-C₁₀ alkyl,C₅-C₇ cycloalkyl, C₆-C₁₅ aryl, and alkylaryl with C₁-C₁₀ alkyl andC₆-C₁₅ aryl, or any two neighboring substituents may form a cyclicsaturated or non-saturated C₄-C₁₀ ring.

A substituted cyclopentadienyl may for example be represented by thegeneral formula C₅R³R⁴R⁵R⁶. A substituted indenyl may for example berepresented by the general formula C₉R⁷R⁸R⁹R¹⁰R¹¹R¹²R¹³R¹⁴. Asubstituted tetrahydroindenyl may for example be represented by thegeneral formula C₉H₄R¹⁵R¹⁶R¹⁷R¹⁸. A substituted fluorenyl may forexample be represented by the general formula C₁₃R¹⁹ _(R)²⁰R²¹R²²R²³R²⁴R²⁵R²⁶. Each of the substituents R³ to R²⁶ mayindependently be selected from the group consisting of hydrogen, C₁-C₁₀alkyl, C₅-C₇ cycloalkyl, C₆-C₁₅ aryl, and alkylaryl with C₁-C₁₀ alkyland C₆-C₁₅ aryl, or any two neighboring R may form a cyclic saturated ornon-saturated C₄-C₁₀ ring; provided, however, that not all substituentssimultaneously are hydrogen.

Preferred metallocene components are those having C₂-symmetry or thosehaving C₁-symmetry. Most preferred are those having C₂-symmetry.

Particularly suitable metallocene components are those wherein R^(b) andR^(c) are the same and are substituted cyclopentadienyl, preferablywherein the cyclopentadienyl is substituted in the 2-position, the3-position, or simultaneously the 2-position and the 3-position.

Particularly suitable metallocene components are also those whereinR^(b) and R^(c) are the same and are selected from the group consistingof unsubstituted indenyl, unsubstituted tetrahydroindenyl, substitutedindenyl and substituted tetrahydroindenyl. Substituted indenyl ispreferably substituted in the 2-position, the 3-position, the4-position, the 5-position or any combination of these, more preferablyin the 2-position, the 4-position or simultaneously in the 2-positionand the 4-position. Substituted tetrahydroindenyl is preferablysubstituted in the 2-position, the 3-position, or simultaneously the2-position and the 3-position.

Particularly suitable metallocene components may also be those whereinR^(b) is a substituted cyclopentadienyl and R^(c) is a substituted orunsubstituted fluorenyl. The substituted cyclopentadienyl is preferablysubstituted in the 2-position, the 3-position, the 5-position orsimultaneously any combination of these, more preferably in the3-position or the 5-position or both simultaneously, most preferably inthe 3-position only, with a bulky substituent. Said bulky substituentmay for example be —CR²⁷R²⁸R²⁹ or —SiR²⁷R²⁸R²⁹ with R²⁷, R²⁸ and R²⁹independently selected from group consisting of C₁-C₁₀ alkyl, C₅-C₇cycloalkyl, C₆-C₁₅ aryl, and alkylaryl with C₁-C₁₀ alkyl and C₆-C₁₅aryl, or any two neighboring R may form a cyclic saturated ornon-saturated C₄-C₁₀ ring. it is preferred that R²⁷, R²⁸ and R²⁹ aremethyl.

Examples of particularly suitable metallocenes are:

dimethylsilanediyl-bis(2-methyl-cyclopentadienyl)zirconium dichloride,

dimethylsilanediyl-bis(3-methyl-cyclopentadienyl)zirconium dichloride,

dimethylsilanediyl-bis(3-tert-butyl-cyclopentadienyl)zirconiumdichloride,

dimethylsilanediyl-bis(3-tert-butyl-5-methyl-cyclopentadienyl)zirconiumdichloride,

dimethylsilanediyl-bis(2,4-dimethyl-cyclopentadienyl)zirconiumdichloride,

dimethylsilanediyl-bis(indenyl)zirconium dichloride,

dimethylsilanediyl-bis(2-methyl-indenyl)zirconium dichloride,

dimethylsilanediyl-bis(3-methyl-indenyl)zirconium dichloride,

dimethylsilanediyl-bis(3-tert-butyl-indenyl)zirconium dichloride,

dimethylsilanediyl-bis(4,7-dimethyl-indenyl)zirconium dichloride,

dimethylsilanediyl-bis(tetrahydroindenyl)zirconium dichloride,

dimethylsilanediyl-bis(benzindenyl)zirconium dichloride,

dimethylsilanediyl-bis(3,3′-2-methyl-benzindenyl)zirconium dichloride,

dimethylsilanediyl-bis(4-phenyl-indenyl)zirconium dichloride,

dimethylsilanediyl-bis(2-methyl-4-phenyl-indenyl)zirconium dichloride,

ethanediyl-bis(indenyl)zirconium dichloride,

ethanediyl -bis(tetrahydroindenyl)zirconium dichloride,

isopropylidene-(3-tert-butyl-cyclopentadienyl)(fluorenyl) zirconiumdichloride

isopropylidene-(3-tert-butyl-5-methyl-cyclopentadienyl)(fluorenyl)zirconium dichloride.

The metallocene may be supported according to any method known in theart. In the event it is supported, the support used in the presentinvention can be any organic or inorganic solid, particularly poroussupports such as talc, inorganic oxides, and resinous support materialsuch as polyolefin. Preferably, the support material is an inorganicoxide in its finely divided form.

The metallocene propylene random copolymer used herein is produced bypolymerizing propylene and at least one comonomer in presence of ametallocene-based polymerization catalyst to obtain a metallocene randomcopolymer of propylene and at least one comonomer. The polymerization ofpropylene and the at least one comonomer in presence of ametallocene-based polymerization catalyst can be carried out accordingto known techniques in one or more polymerization reactors attemperatures in the range from 20° C. to 150° C. The metallocenepropylene random copolymer used herein is preferably produced bypolymerization in liquid propylene at temperatures in the range from 20°C. to 120° C. More preferred temperatures are in the range from 60° C.to 100° C. The pressure can be atmospheric or higher. It is preferablybetween 25 and 50 bar. The molecular weight of the polymer chains, andin consequence the melt flow of the resulting metallocene propylenerandom copolymer, may be controlled by the addition of hydrogen to thepolymerization medium.

Preferably, the metallocene propylene random copolymer is recovered fromthe one or more polymerization reactors without post-reactor treatment,such as thermal or chemical degradation (e.g. by using peroxides), toreduce its molecular weight and/or narrow the molecular weightdistribution, as is often done for polypropylene produced with aZiegler-Natta catalyst.

Preferably, the polypropylene composition used herein comprises anucleating agent, more specifically an a-nucleating agent. For thepurposes of the present application, a nucleating agent is defined as achemical compound that raises the crystallization temperature of thepolypropylene composition.

Suitable nucleating agents for use in the present invention can beselected from any of the nucleating agents known to the skilled person.It is, however, preferred that the nucleating agent be selected from thegroup consisting of talc, carboxylate salts, sorbitol acetals, phosphateester salts, substituted benzene tricarboxamides and polymericnucleating agents, as well as blends of these.

Examples for carboxylate salts are organocarboxylic acid salts.Particular examples are sodium benzoate and lithium benzoate. Theorganocarboxylic acid salts may also be alicyclic organocarboxylic acidsalts, preferably bicyclic organodicarboxylic acid salts and morepreferably a bicyclo[2.2.1]heptane dicarboxylic acid salt. A nucleatingagent of this type is sold as HYPERFORM® HPN-68 by Milliken Chemical.

Examples for sorbitol acetals are dibenzylidene sorbitol (DBS),bis(p-methyl-dibenzylidene sorbitol) (MDBS), bis(p-ethyl-dibenzylidenesorbitol), bis(3,4-dimethyl-dibenzylidene sorbitol) (DMDBS), andbis(4-propylbenzylidene) propyl sorbitol. Bis(3,4-dimethyl-dibenzylidenesorbitol) (DMDBS) and bis(4-propylbenzylidene) propyl sorbitol arepreferred. These can for example be obtained from Milliken Chemicalunder the trade names of Millad 3905, Millad 3940, Millad 3988 andMillad NX8000.

Examples of phosphate ester salts are salts of2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate. Such phosphateester salts are for example available as NA-11 or NA-21 from AsahiDenka.

Examples of substituted tricarboxam ides are those of general formula(II)

wherein R1, R2 and R3 as indicated in formula (II), independently of oneanother, are selected from C₁-C₂₀ alkyls, C₅-C₁₂ cycloalkyls, or phenyl,each of which may in turn by substituted with C₁-C₂₀ alkyls, C₅-C₁₂cycloalkyls, phenyl, hydroxyl, C₁-C₂₀ alkylamino or C₁-C₂₀ alkyloxy etc.Examples for C₁-C₂₀ alkyls are methyl, ethyl, n-propyl, n-butyl,iso-butyl, tert-butyl, n-pentyl, iso-pentyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, 3-methylbutyl, hexyl, heptyl, octyl or1,1,3,3-tetramethylbutyl. Examples for C₅-C₁₂ cycloalkyl arecyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, adamantyl,2-methylcyclohexyl, 3-methylcyclohexyl or 2,3-dimethylcyclohexyl. Suchnucleating agents are disclosed in WO 03/102069 and by Blomenhofer etal. in Macromolecules 2005, 38, 3688-3695. A specific example of such anucleating agent isN,N′,N″-tris(2-methylcyclohexyl)-1,2,3-propanetricarboxamide, which isfor example commercially available from Rika International Limited underthe tradename RIKACLEAR PC1.

Examples of polymeric nucleating agents are polymeric nucleating agentscontaining vinyl compounds, which are for example disclosed inEP-A1-0152701 and EP-A2-0368577. The polymeric nucleating agentscontaining vinyl compounds can either be physically or chemicallyblended with the metallocene random copolymer of propylene and one ormore comonomers. In physical blending the polymeric nucleating agentcontaining vinyl compounds is mixed with the metallocene randomcopolymer of propylene and one or more comonomers in an extruder or in ablender. In chemical blending the metallocene random copolymer ofpropylene and one or more comonomers comprising the polymeric nucleatingagent containing vinyl compounds is produced in a polymerization processhaving at least two stages, in one of which the polymeric nucleatingagent containing vinyl compounds is produced. Preferred vinyl compoundsare vinyl cycloalkanes or vinyl cycloalkenes having at least 6 carbonatoms, such as for example vinyl cyclopentane, vinyl-3-methylcyclopentane, vinyl cyclohexane, vinyl-2-methyl cyclohexane,vinyl-3-methyl cyclohexane, vinyl norbornane, vinyl cylcopentene, vinylcyclohexene, vinyl-2-methyl cyclohexene. The most preferred vinylcompounds are vinyl cyclopentane, vinyl cyclohexane, vinyl cyclopenteneand vinyl cyclohexene.

Further examples of polymeric nucleating agents arepoly-3-methyl-1-butene, polydimethylstyrene, polysilanes andpolyalkylxylenes. As explained for the polymeric nucleating agentscontaining vinyl compounds, these polymeric nucleating agents can beintroduced into the metallocene polypropylene either by chemical or byphysical blending.

It is also possible to use high-density polyethylene, or a polypropylenehaving a fractional melt flow, or a polypropylene that comprises afraction of fractional melt flow.

Further, it is possible to use blends of nucleating agents, such as forexample a blend of talc and a phosphate ester salt or a blend of talcand a polymeric nucleating agent containing vinyl compounds.

The nucleating agent may be introduced into the polypropylenecomposition by blending it with a nucleating agent, which is either inpure form or in form of a masterbatch, for example by dry-blending or bymelt-blending. It is within the scope of the present invention that thenucleating agent can be introduced into the polypropylene composition byblending it with a thermoplastic polymer comprising a nucleating agent,wherein said thermoplastic polymer is different from the metallocenerandom copolymer as defined above.

While it is clear to the skilled person that the amount of nucleatingagent to be added depends upon its crystallization efficiency, for thepurposes of the present invention the nucleating agent or the blend ofnucleating agents—if comprised at all—is present in the polypropylenecomposition in an amount of at least 50 ppm, preferably at least 100ppm. It is present in an amount of at most 5000 ppm, preferably of atmost 4000 ppm, even more preferably of at most 3000 ppm and mostpreferably of at most 2000 ppm.

The polypropylene composition used herein may also comprise furtheradditives, such as by way of example, antioxidants, light stabilizers,acid scavengers, lubricants, antistatic additives, and colorants. Anoverview of such additives may be found in Plastics Additives Handbook,ed. H. Zweifel, 5th edition, 2001, Hanser Publishers.

The polypropylene composition used herein may further comprise one ormore thermoplastic polymers different from the random copolymer ofpropylene and at least comonomer produced with a metallocene-basedpolymerization catalyst as described above.

Irrespectively of the number of components, which are comprised in thepolypropylene composition, it is understood that their weightpercentages, relative to the total weight of the polypropylenecomposition, add up to 100 wt %.

Preferred suitable thermoplastic polymers that may be used herein may beselected from the group consisting of polyolefins, polyamides andpolyesters, with the provision that said polyolefin is different fromthe propylene random copolymer used herein. By “different from thepropylene random copolymer” is meant that the polyolefin differs in atleast one characteristic from the above defined propylene randomcopolymer. Said polyolefin may for example be different in composition,such as for example be based on an alpha-olefin different from propylene(e.g. ethylene, 1-butene, 1-pentene, 1-hexene or 1-octene), or beproduced with a Ziegler-Natta catalyst instead of a metallocene-basedpolymerization catalyst, or have a different type of comonomer or have adifferent content of comonomer.

Exemplary polyolefins for use herein are olefin homopolymers andcopolymers of an olefin and one or more comonomers. The polyolefins maybe atactic, syndiotactic or isotactic. The olefin can for example beethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-penteneor 1-octene, but also cycloolefins such as for example cyclopentene,cyclohexene, cyclooctene or norbornene. The comonomer is different fromthe olefin and chosen such that it is suited for copolymerization withthe olefin. The comonomer may also be an olefin as defined above.Further examples of suitable comonomers are vinyl acetate(H₃C—C(═O)O—CH═CH₂) or vinyl alcohol (“HO—CH═CH₂”, which as such is notstable and tends to polymerize). Examples of olefin copolymers suitedfor use in the present invention are random copolymers of propylene andethylene, random copolymers of propylene and 1-butene, heterophasiccopolymers of propylene and ethylene, ethylene-butene copolymers,ethylene-hexene copolymers, ethylene-octene copolymers, copolymers ofethylene and vinyl acetate (EVA), copolymers of ethylene and vinylalcohol (EVOH).

Exemplary polyamides for use herein may be characterized in that thepolymer chain comprises amide groups (—NH—C(═O)—). Polyamides useful inthe present invention are preferably characterized by one of thefollowing chemical structures

wherein m and n may be independently chosen from one another and be aninteger from 1 to 20.

Specific examples of suitable polyamides are polyamides 4, 6, 7, 8, 9,10, 11, 12, 46, 66, 610, 612, or 613. Another example of a suitablepolyamide is Nylon-MXD6, obtainable by polycondensation of meta-xylylenediamine with adipic acid and commercially available for example fromMitsubishi Gas Chemical Company.

Exemplary polyesters for use herein are preferably characterized by thefollowing chemical structure

[—C(═O)—C₆H₄—C(═O)O—(CH₂—CH₂)_(n)—O—]_(x)

wherein n is an integer from 1 to 10, with preferred values being 1 or2.

Specific examples of suitable polyesters are polyethylene terephthalate(PET) and polybutylene terephthalate (PBT).

Furthermore, preferred polyesters are poly(hydroxy carboxylic acid)s.

With respect to the melt flow index of the polypropylene composition, itis preferred that it is within the same ranges and values as definedabove for the random copolymer of propylene and at least one comonomer,produced in presence of a metallocene-based polymerization catalyst, asdefined in the present application.

Production of Extrusion Blow-Molded Articles

Extrusion blow-molded articles may be produced by melt-extruding apolypropylene composition as defined above to produce a parison ofmolten polypropylene composition, wherein the polypropylene compositioncomprises a propylene random copolymer having been produced bypolymerizing propylene and at least one comonomer with ametallocene-based polymerization catalyst as defined above. The parisonof molten polypropylene composition is clamped into a mold so that theparison is closed-off at both ends, i.e. forms a closed hollow volumeinside. In the following, gas (such as air, nitrogen or any other inertgas) under pressure is injected into the closed-off parison so that theparison is expanded to take the shape of the mold, thus obtaining anexpanded parison having the shape of the mold, which is subsequentlycooled, and finally the extrusion blow-molded article is ejected. A moredetailed description of the extrusion blow-molding process may forexample be found in N.C. Lee, Practical Guide to Blow Moulding, RapraTechnology Limited, Shrewsbury, 2006.

Hence, the present application provides for the production of extrusionblow-molded articles by a process comprising the following steps:

(a) polymerizing propylene and at least one comonomer with ametallocene-based polymerization catalyst to obtain a random copolymerof propylene and at least one comonomer, wherein the random copolymercomprises at most 7.0 wt %, relative to the total weight of said randomcopolymer, of the at least one comonomer;

(b) melt-extruding a polypropylene composition comprising the randomcopolymer prepared in step (a) to form a parison of molten polypropylenecomposition;

(c) clamping the parison into a mold so that the parison is closed offat both ends to form a clamped-off parison;

(d) injecting a gas under pressure into the clamped-off parison toobtain an expanded parison having the shape of the mold;

(e) finally cooling and ejecting the extrusion blow-molded article.

Preferably, in step (b) of said process the melt-extrusion of thepolypropylene composition is done at a temperature of the moltenpolypropylene composition that is higher than the melting temperatureT_(melt) of said polypropylene composition. More preferably, thetemperature of the molten polypropylene composition is at leastT_(melt)+5° C., and most preferably at least T_(melt)+10° C., withT_(melt) being the melting temperature of the polypropylene composition.Preferably, in step (b) of said process the melt-extrusion of thepolypropylene composition is done at a temperature of the moltenpolypropylene composition of at most T_(melt)+50° C., more preferably ofat most T_(melt)+40° C., even more preferably of at most T_(melt)+30°C., still even more preferably of at most T_(melt)+25° C., and mostpreferably of at most T_(melt)+20° C., provided that the temperature ofthe molten polypropylene composition is at most 180° C., and mostpreferably at most 170° C. The melting temperature T_(melt) of therandom copolymer is determined by DSC as described in the test methods.

In addition to the polypropylene layer as described above, the extrusionblow-molded article may also comprise a further layer consisting of athermoplastic polymer composition. Said thermoplastic polymercomposition comprises a thermoplastic polymer selected from the groupconsisting of polyolefins, polyamides, polyesters and blends of these,with the provision that said thermoplastic polymer composition isdifferent from the polypropylene composition as defined above.Preferably, said thermoplastic polymer is a polyamide or a polyethylene.Most preferably, it is a polyethylene, i.e. that the extrusionblow-molded article comprises a polyethylene layer. Suitablepolyolefins, polyamides and polyester are as described above.

The present extrusion blow-molded article is useful in packagingapplications, for example in food packaging, detergent packaging,cosmetic packaging, paint packaging, and medical packaging. Examples offood packaging are packaging for juices, dried foods, sweets, candies,nuts, milk products. Examples of detergent packaging are packaging forwashing powders, dish soap, household cleaners. Examples of cosmeticpackaging are packaging for shower gels, shampoos, oils, cremes, liquidsoaps. Examples for medical packaging are packaging for pills,solutions, disinfectants.

Test Methods

The melt flow index (MFI) of polypropylene and polypropylenecompositions is determined according to ISO 1133, condition L, at 230°C. and 2.16 kg.

Molecular weights are determined by Size Exclusion Chromatography (SEC)at high temperature (145° C.). A 10 mg polypropylene is dissolved at160° C. in 10 ml of trichlorobenzene (technical grade) for 1 hour.Analytical conditions for the GPCV 2000 from WATERS are:

Injection volume: +/−400 μl

Automatic sample preparation and injector temperature: 160° C.

Column temperature: 145° C.

Detector temperature: 160° C.

Column set: 2 Shodex AT-806MS and 1 Styragel HT6E

Flow rate: 1 ml/min

Detector: Infrared detector (2800-3000 cm⁻¹)

Calibration: Narrow standards of polystyrene (commercially available)

Calculation for polypropylene: Based on Mark-Houwink relation(log₁₀(M_(PP))=log₁₀(M_(PS))−0.25323); cut off on the low molecularweight end at M_(PP)=1000.

The molecular weight distribution (MWD) is then calculated asM_(w)/M_(n).

The ¹³C-NMR analysis is performed using a 400 MHz Bruker NMRspectrometer under conditions such that the signal intensity in thespectrum is directly proportional to the total number of contributingcarbon atoms in the sample. Such conditions are well known to theskilled person and include for example sufficient relaxation time etc.In practice the intensity of a signal is obtained from its integral,i.e. the corresponding area. The data is acquired using protondecoupling, 4000 scans per spectrum, a pulse repetition delay of 20seconds and a spectral width of 26000 Hz. The sample is prepared bydissolving a sufficient amount of polymer in 1,2,4-trichlorobenzene(TCB, 99%, spectroscopic grade) at 130° C. and occasional agitation tohomogenize the sample, followed by the addition of hexadeuterobenzene(C₆D₆, spectroscopic grade) and a minor amount of hexamethyldisiloxane(HMDS, 99.5+%), with HMDS serving as internal standard. To give anexample, about 200 mg of polymer are dissolved in 2.0 ml of TCB,followed by addition of 0.5 ml of C₆D₆ and 2 to 3 drops of HMDS.

Following data acquisition the chemical shifts are referenced to thesignal of the internal standard HMDS, which is assigned a value of 2.03ppm.

The isotacticity is determined by ¹³C-NMR analysis on the total polymer.In the spectral region of the methyl groups the signals corresponding tothe pentads mmmm, mmmr, mmrr and mrrm are assigned using published data,for example A. Razavi, Macromol. Symp., vol. 89, pages 345-367. Only thepentads mmmm, mmmr, mmrr and mrrm are taken into consideration due tothe weak intensity of the signals corresponding to the remainingpentads. For the signal relating to the mmrr pentad a correction isperformed for its overlap with a methyl signal related to2,1-insertions. The percentage of mmmm pentads is then calculatedaccording to

% mmmm=AREA_(mmmm)/(AREA_(mmmm)+AREA_(mmmr)+AREA_(mmrr)+AREA_(mrrm))·100

Determination of the percentage of 2,1-insertions for a metallocenepropylene homopolymer: The signals corresponding to the 2,1-insertionsare identified with the aid of published data, for example H. N. Cheng,J. Ewen, Makromol. Chem., vol. 190 (1989), pages 1931-1940. A firstarea, AREA1, is defined as the average area of the signals correspondingto 2,1-insertions. A second area, AREA2, is defined as the average areaof the signals corresponding to 1,2-insertions. The assignment of thesignals relating to the 1,2-insertions is well known to the skilledperson and need not be explained further. The percentage of2,1-insertions is calculated according to

2,1-insertions(in %)=AREA1/(AREA1+AREA2)˜100

with the percentage in 2,1-insertions being given as the molarpercentage of 2,1-inserted propylene with respect to total propylene.

The determination of the percentage of 2,1-insertions for a metallocenerandom copolymer of propylene and ethylene is determined by twocontributions:

(i) the percentage of 2,1-insertions as defined above for the propylenehomopolymer, and

(ii) the percentage of 2,1-insertions, wherein the 2,1-insertedpropylene neighbors an ethylene,

thus the total percentage of 2,1-insertions corresponds to the sum ofthese two contributions. The assignments of the signal for case (ii) canbe done either by using reference spectra or by referring to thepublished literature.

Melting temperatures T_(melt) are measured on a DSC Q2000 instrument byTA Instruments based on ISO 3146. To erase the thermal history thesamples are first heated to 200° C. and kept at 200° C. for a period of3 minutes. The reported melting temperatures T_(melt) are thendetermined with heating and cooling rates of 20° C./min.

EXAMPLES

The advantages of the present invention are illustrated by the followingexamples using

(i) a random copolymer of propylene and ethylene (denoted as “PP-1”)having been produced in a bulk loop reactor using a supportedmetallocene-based polymerization catalyst with a dimethylsilyl-bridgedbis(indenyl) zirconium dichloride derivative as metallocene component,and

(ii) a random copolymer of propylene and ethylene (denoted as “PP-2”)having been produced in a bulk loop reactor using a commercialZiegler-Natta polymerization catalyst.

Both, PP-1 and PP-2 contained a nucleating agent as well as sufficientamounts of antioxidants and acid scavenger to reduce their degradationin melt-processing. Additional properties of PP-1 and PP-2 are given inTable 1.

TABLE 1 Comparative Example example Product Unit PP-1 PP-2 Ethylenecontent wt % 2.0 3.4 MFI dg/min 10 1.8 M_(w)/M_(n) 2.7 7.7 Meltingtemperature T_(melt) ° C. 138.2 145.8 2,1-insertions 0.7 0

Single-layer bottles with a volume of 430 ml were extrusion blow-moldedon a Kautex KEB extrusion blow molding machine with a screw having aratio of length over diameter (L/D) of 25. Processing conditions aregiven in Table 2.

Very surprisingly the metallocene random copolymer as defined in thepresent application allowed the production of bottles having goodmechanical and optical properties at much lower extruder and dietemperatures, and consequentially at lower melt temperatures as comparedto a comparative random copolymer produced with a Ziegler-Nattapolymerization catalyst. Such difference in processability results insignificant energy savings while allowing to produce bottles havingcomparable properties.

Based on these results, it is anticipated that the present inventionwill in a general way allow to produce extrusion blow-molded articles ata higher throughput than a conventional extrusion blow-molding processwith a polypropylene commonly used in extrusion blow-molding.

TABLE 2 Comparative Example example Product Unit PP-1 PP-2 Extrudertemperatures Zone 1 ° C. 150 188 Zone 2 ° C. 150 190 Zone 3 ° C. 150 192Zone 4 ° C. 150 195 Zone 5 ° C. 150 210 Zone 6 ° C. 150 210 Dietemperature ° C. 155 210 Temperature of the melt ° C. 152 205 Moldcooling water temp. ° C. 15 15 Blowing time s 7 7 Blowing pressure bar8.6 8.6 Total cycle time s 12.6 13.0 Throughput kg/h 10.0 10.1 Bottleweight g 20.3 20.1

1.-15. (canceled)
 16. A process for the production of an extrusionblow-molded article, said process comprising the steps of (a)polymerizing propylene and at least one comonomer with ametallocene-based polymerization catalyst to obtain a random copolymerof propylene and at least one comonomer, wherein the random copolymerhas a molecular weight distribution, defined as Mw/Mn, of at most 4.0, apercentage of 2,1-insertions of at least 0.1%, relative to the totalnumber of propylene molecules in the chain, and comprises at most 7.0 wt%, relative to the total weight of said random copolymer, of the atleast one comonomer; (b) melt-extruding a polypropylene compositioncomprising the random copolymer prepared in step (a) to form a parisonof said molten polypropylene composition; (c) clamping the parison intoa mold so that the parison is closed off at both ends to form aclamped-off parison; (d) injecting a gas under pressure into saidclamped-off parison to obtain an expanded parison having the shape ofthe mold; (e) finally cooling and ejecting the extrusion blow-moldedarticle.
 17. The process according to claim 16, characterized in that instep (b) the polypropylene composition is melt-extruded at a temperatureof the molten polypropylene composition of at least Tmelt+5° C., withTmelt being the melting temperature of the polypropylene compositiondetermined by DSC.
 18. The process according to claim 16, wherein instep (e) the polypropylene composition is extruded at a temperature ofthe molten polypropylene composition of at most Tmelt+50° C., providedthat the temperature of the molten polypropylene composition is at most180° C., with Tmelt being the melting temperature of the polypropylenecomposition determined by DSC.
 19. The process according to claim 16,wherein the extrusion blow-molded container and has a wall thickness ofat least 300 μm and of at most 2000 μm
 20. The process according toclaim 16, wherein the random copolymer of propylene and at least onecomonomer comprises at least 0.5 wt % and at most 7.0 wt %, relative tothe total weight of said random copolymer, of the at least onecomonomer.
 21. The process according to claim 16, wherein the randomcopolymer of propylene and at least one comonomer is a random copolymerof propylene and at least one alpha-olefin different from propylene. 22.The process according to claim 21, wherein the alpha-olefin is selectedfrom the group consisting of ethylene, butene-1, pentene-1, hexene-1 and4-methyl-pentene-1.
 23. The process according to claim 16, wherein therandom copolymer of propylene and at least one comonomer has a melt flowrate of at least 3.0 dg/min, determined according to ISO 1133, conditionL, at 230° C. and 2.16 kg.
 24. The process according to claim 16,wherein the random copolymer of propylene and at least one comonomer hasa melt flow rate of at most 20 dg/min, determined according to ISO 1133,condition L, at 230° C. and 2.16 kg.
 25. The process according to claim16, wherein the random copolymer of propylene and at least one comonomerhas a content of mmmm pentads of at least 90%.
 26. The process accordingto claim 16, wherein the random copolymer of propylene and at least onecomonomer has a melt flow rate of at least 8 dg/min and at most 20dg/min, determined according to ISO 1133, condition L, at 230° C. and2.16 kg.
 27. The process according to claim 16, wherein the randomcopolymer of propylene and at least one comonomer is a metallocenepropylene random copolymer.
 28. The process according to claim 27,wherein the metallocene propylene random copolymer has at least twopropylene polymer fractions.
 29. The process according to claim 28,wherein the at least two propylene polymer fractions differ in comonomercontent, melt flow index, or both.
 30. The process according to claim27, wherein the polypropylene composition comprises one or morethermoplastic polymers different from the metallocene propylene randomcopolymer.
 21. The process according to claim 27, wherein thepolypropylene composition comprises at least 50 wt. %, relative to atotal weight of the polypropylene composition, of the metallocenepropylene random copolymer.
 22. The process according to claim 16,wherein the polypropylene composition comprises a nucleating agent.